Arboretum Botanical Glossary

Ascomycete A fungus that forms its sexual spores inside a special cell called the ascus. Because the ascus is often sac-shaped, the ascomycetes are sometimes referred to as sac fungi. The spores are termed ascospores. Usually there are eight ascospores formed in each ascus, but the number can vary from one to more than one hundred, depending upon the species. The ascomycetes comprise the largest…

Asexual Without sex, often used to describe the propagation of plants by cuttings or grafts. Did you know? Named apple varieties are propagated asexually by grafting, so every tree of that variety produces the same type of fruit.

Attenuate With a long, gradual taper. This feature helps describe plant form, function, or identification.

Auricle A small ear-shaped appendage. This feature helps describe plant form, function, or identification.

Auriculate Bearing ear-like appendages. This feature helps describe plant form, function, or identification.

Avoided Runoff estimates the number of gallons of stormwater runoff each year that is avoided because tree canopies catch rainfall and trees return some water to the atmosphere through evaporation and transpiration. Learn More Surface runoff can be a cause for concern in many urban areas, as it can contribute to pollution of streams, wetlands, rivers, lakes, and oceans. During precipitation events, some portion of…

Awn A narrow bristle-like appendage, usually at the tip or dorsal surface. Did you know? Some grass awns twist and untwist with humidity changes, helping drill the seed into the soil.

Axil The angular connection between a leaf or branch and a stem Did you know? Most new side branches begin from axillary buds, which is why pruning just above a leaf node can encourage branching.

Axillary Located at an axil. This feature helps describe plant form, function, or identification.